Pre-heat oven to 375 and line a jumbo muffin tins with papers or grease lightly. If you prefer standard-size muffins, use a regular size muffin/cupcake tin.
Combine flour, baking powder, and sugar in a large bowl and make a well in the center.
Put melted butter in a large bowl. Stir in yogurt and water. Then add the eggs, stirring well after each addition.
Pour the wet ingredients into the well in dry ingredients and stir to combine, taking care not to over-mix. Fold chocolate and raspberries into the batter.
Divide batter evenly between cavities of the prepared tins, filling each about ¾ of the way full.
Bake 27-30 minutes for jumbo muffins, until tops are just turning golden. If making standard-size muffins, bake for 20-23 minutes.
Let cool in pan for a few minutes before removing to a wire rack to cool completely. Once cool, sprinkle with confectioners' sugar.